package org.apache.lucene.search;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/** Lower-level search API.
 * <br>HitCollectors are primarily meant to be used to implement queries,
 * sorting and filtering.
 * @see Searcher#search(Query,HitCollector)
 * @version $Id: HitCollector.java 155607 2005-02-27 01:29:53Z otis $
 */
public abstract class HitCollector {
    /** Called once for every non-zero scoring document, with the document number
     * and its score.
     *
     * <P>If, for example, an application wished to collect all of the hits for a
     * query in a BitSet, then it might:<pre>
     *   Searcher searcher = new IndexSearcher(indexReader);
     *   final BitSet bits = new BitSet(indexReader.maxDoc());
     *   searcher.search(query, new HitCollector() {
     *       public void collect(int doc, float score) {
     *         bits.set(doc);
     *       }
     *     });
     * </pre>
     *
     * <p>Note: This is called in an inner search loop.  For good search
     * performance, implementations of this method should not call
     * {@link Searcher#doc(int)} or
     * {@link org.apache.lucene.index.IndexReader#document(int)} on every
     * document number encountered.  Doing so can slow searches by an order
     * of magnitude or more.
     * <p>Note: The <code>score</code> passed to this method is a raw score.
     * In other words, the score will not necessarily be a float whose value is
     * between 0 and 1.
     */
    public abstract void collect(int doc, float score);
}
